Text::Header - RFC 822/2068 "header" and "unheader" functions

       Copyright (c) 2000 Nathan Wiger <nate@sun.com>. All Rights Reserved.

       This module is free software; you may copy this under the terms of the GNU General Public License, or the
       Artistic License, copies of which should have accompanied your Perl kit.

perl v5.34.0                                       2022-06-28                                        Header(3pm)

       This module provides two new functions, "header" and "unheader", which provide general-purpose RFC 822
       header construction and parsing.  They do not provide any intelligent defaults of HTTP-specific methods.
       They are simply aimed at providing an easy means to address the mechanics of header parsing.

       The output style is designed to mimic "CGI.pm" and "HTTP::Headers", so that users familiar with these
       interfaces will feel at home with these functions. As shown above, the "headers" function automatically
       does the following:

          1. uc's the first letter of each tag token and lc's the
             rest, also converting _'s to -'s automatically

          2. Adds a colon separating each tag and its value, and
             exactly one newline after each one

          3. Combines list elements into a comma-delimited
             string

       Note that a list is always joined into a comma-delimited string. To insert multiple separate headers,
       simply call "header" with multiple args:

          push @out, header(accept => 'text/html',
                            accept => 'text/plain');

       This would create multiple "Accept:" lines.

       Note that unlike "CGI.pm", the "header" function provided here does not provide any intelligent defaults.
       If called as:

           @out_headers = header;

       It will return an empty list. This allows "header" to be more general pupose, so it can provide SMTP and
       other headers as well. You can also use it as a generic text formatting tool, hence the reason it's under
       the "Text::" hierarchy.

       The "unheader" function works in exactly the opposite direction from "header", pulling apart headers and
       returning a list. "unheader":

          1. lc's the entire tag name, converting -'s to _'s

          2. Separates each tag based on the colon delimiter,
             chomping newlines.

          3. Returns a list of tag/value pairs for easy assignment
             to a hash

       So, assuming the @HEADERS array shown up top:

          %myheaders = unheader(@HEADERS);

       The hash %myheaders would have the following values:

          %myheaders = (
              content_type => 'text/html',
              author => 'Nathan Wiger',
              last_modified => 'Wed Sep 27 13:31:06 PDT 2000',
              accept => 'text/html, text/plain'
          );

       Note that all keys are converted to lowercase, and their values have their newlines stripped. However,
       note that comma-separated fields are not split up on input. This cannot be done reliably because some
       fields, such as the HTTP "Date:" header, can contain commas even though they are not lists. Inferring
       this type of structure would require knowledge of content, and these functions are specifically designed
       to be content-independent.

       The "unheader" function will respect line wrapping, as seen in SMTP headers. It will simply join the
       lines and return the value, so that:

          %mail = unheader("To: Nathan Wiger <nate@sun.com>,
                                    perl5-porters@perl.org");

       Would return:

          $mail{to} = "Nathan Wiger <nate@sun.com>, perl5-porters@perl.org"

       Notice that multiple spaces between the comma separator have been condensed to a single space. Since the
       "header" and "unheader" functions are direct inverses, this call:

          @out = header unheader @in;

       Will result in @out being exactly equivalent to @in.

       Text::Header - RFC 822/2068 "header" and "unheader" functions

       This is designed as both a Perl 5 module and also a Perl 6 prototype.  Please see the Perl 6 proposal at
       http://dev.perl.org/rfc/333.html

       This module is designed to be fully compliant with the internet standards RFC 822 (SMTP Headers) and RFC
       2068 (HTTP Headers).

          use Text::Header;     # header and unheader exported

          # Construct headers similar to CGI.pm and HTTP::Headers

          @HEADERS = header(content_type => 'text/html',
                            author => 'Nathan Wiger',
                            last_modified => $date,
                            accept => [qw(text/html text/plain)]);

          # The above produces the array:

          @HEADERS = ("Content-Type: text/html\n",
                      "Author: Nathan Wiger\n",
                      "Last-Modified: Wed Sep 27 13:31:06 PDT 2000\n",
                      "Accept: text/html, text/plain\n");

          # Can also construct SMTP headers to format mail

          @mail_headers = header(from => 'Nathan Wiger <nate@sun.com>',
                                 to => 'perl5-porters@perl.org');

          print $MAIL @mail_headers, "\nKeep up the great work!\n";

          # The above would print this to the $MAIL handle:

          From: Nathan Wiger <nate@sun.com>
          To: perl5-porters@perl.org

          Keep up the great work!